The present invention relates to the perfume industry. It concerns more particularly decalin ketones of formula ##STR2## having a single or double bond in one of the positions indicated by the dotted lines, or two double bonds in positions 2 and 5 or 3 and 5 such as indicated by the dotted lines, and wherein symbols R.sup.1, R.sup.2 and R.sup.3 represent a hydrogen atom or a methyl radical, with the exclusion of perhydro-4a,8,8-trimethyl-1-trans-naphthalenone as well as a process for their preparation.
There are many fragrant compounds with a decalin structure known to this day. In particular, a variety of decalin ketones having a more or less similar structure to that of ketones (I) are described in the prior art. G. Ohloff, for example, has described in a review article the odor properties of quite a few of these known compounds and analyzed their properties in the context of a wider study of structure-activity relationships in compounds which develop ambergris-type odor notes [see Fragrance Chemistry: The Sense of Smell, page 535, ed. E. T. Theimer, AP, USA (1982) and references therein].
The majority of these prior art decalin ketones, whose structure is analogous or homologous to that of compounds (I) according to the invention, posses the carbonyl group in a less encumbered ring position and/or in a position further away from the dimethyl group than in formula (I). This is a result of the fact that, up until now, there were no processes available allowing the industrial preparation of pure decalin ketones of formula (I).
Amongst the ketones of formula (I), only perhydro-4a,8,8-trimethyl-1-trans-naphthalenone, having the formula ##STR3## has been described in the prior art, namely by G. Ohloff [ref. cited]. However, the compound disclosed by this author was obviously not obtained in a pure state, since its odor, described as strongly resinous, varnish-like with a musty undertone, is said to be partly due to the olfactive contribution of an analogous ketone of formula On the other hand, A. K. Banerjee et al. [see Tetrahedron 37, 2749 (1981) and J. Chem. Soc. Perkin Trans. I 1982, 2547] described the preparation of ketone (A) and its use in the synthesis of the following decalin ketones: ##STR4## According to these authors, the latter ketones can only be obtained in good yield following an elaborate multi-step process, presenting only an academic interest. In addition, the starting ketone of formula (A) is obtained by means of a process having at least four steps, one of said steps being a reaction of hydroboration-oxidation of an octalin which, for safety reasons, cannot be applied industrially. Likewise, the preparation of said octalin involves reactions which are unsuitable for an industrial synthesis of this compound.
Finally, the above-cited prior art process for the preparation of ketone (A) does not allow the preparation of unsaturated ketones of formula (I) or, at least, it requires further steps which would render the synthesis of these compounds even less adapted to industrial exploitation.
It should be mentioned that Banerjee et al. described only the synthesis of the above-cited compounds and did not suggest any useful application, from an olfactive point of view, of said compounds.